Für jeden Spinner Textfarbe und Textgröße einstellen

<resources>
    <!-- Base  styles.xml-->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
     <item name="android:spinnerItemStyle">@style/mySpinnerItemSelectedStyle</item>
    </style>


    <style name="mySpinnerItemSelectedStyle"
        parent="@android:style/Widget.Holo.TextView.SpinnerItem">
        <item name="android:textColor">#0BCC0B</item>
        <item name="android:background">#000</item>
        <item name="android:textSize">24sp</item>
    </style>




</resources>

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout


xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000"
android:gravity="center_horizontal|left"
tools:context=".MainActivity">


<Spinner
android:id="@+id/spinner_ISO"
android:layout_width="90dp"
android:layout_height="55dp"
android:gravity="center"
android:spinnerMode="dropdown"
android:textSize="20sp"
app:layout_constraintStart_toEndOf="parent "
app:layout_constraintTop_toTopOf="parent" />


<Spinner
android:id="@+id/spinner_Tipps"
android:layout_width="390dp"
android:layout_height="45dp"
android:layout_marginStart="4dp"
android:layout_marginLeft="4dp"


android:textSize="12sp"
android:layout_marginTop="8dp"
android:layout_weight="1"
android:entries="@array/tipp_arrays"
android:gravity="top"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="parent" />


</androidx.constraintlayout.widget.ConstraintLayout>